Nitrogen and boron coordinated single-atom catalysts for low-temperature CO/NO oxidations

Abstract

In order to explore the intrinsic properties of single-atom (SA) catalysts, the different kinds of coordinated atoms (typically B_x and N_y) within graphene (B_xN_y–graphene, x + y = 1–3) can be used to regulate the stability and electronic structure of center metal SAs (B_xN_y–graphene-SAs) by density functional theory (DFT) calculations. It is found that the SA Co anchored at single vacancy graphene (SV-graphene–Co), B₁–graphene–Co and N₁–graphene–Co configurations exhibit higher stability than others. The amount of charge transfer between coordinated B_xN_y and nearest-neighbor carbon atoms can effectively modulate the adsorption stabilities, electronic structures and magnetic properties of central Co atom and reactive gases. Compared to the SV-graphene–Co sheet, the formation of B_xN_y–graphene sheets can promote the adsorption capabilities for NO and CO; further, the NO and CO oxidation reactions through the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms are comparably investigated. Among these different ratios of coordinated B_xN_y atoms, the B₁–graphene–Co, N₁–graphene–Co and B₁N₁–graphene–Co sheets exhibit good stability and show excellent catalytic activity (<0.5 eV). Therefore, theoretical calculations can provide an in-depth understanding of the structure–performance relationship between coordinated B/N atoms and intrinsic activity of SA catalysts (SACs), which is essential for the precise design of graphene-based SACs and their potential applications.